1. Field of the Invention
The invention relates to the techniques of compressing and then winding fibrous mats in order to make it possible to package and condition them until they reach their place of use. Flexible fibrous mats, especially those which consist of glass wool or rock wool and are intended for insulation, are usually wound on themselves in a very close-packed manner, so as to avoid them occupying too large a volume while being transported. The higher the compression ratio of the mat, the less costly are transport and storage.
2. Description of the Related Art
In general, the production lines operate continuously and deliver mats of uninterrupted length. These mats are cut in order to form rolls, the width and length of which correspond to the user's requirements. On the production lines for mats of insulating wool, there are winding machines which operate in a more or less automated manner.
In order to perform their functions, these machines must have some basic characteristics. They must compress the wool mats as much as possible in the same way over their entire length, but they must also avoid damaging the fibre and binder forming the insulating mat.
Moreover, it is important for all the operations to take place at sufficient speed to be compatible with the speed of travel of the mat. This is a particularly important point as regards modern lines where it is often desirable to increase the production capacity. For this purpose, the number of upstream units producing glass or rock fibres is increased, all these units successively feeding the same mat, the speed of travel of which depends, all else being equal, on the number of machines upstream.
In order to reduce transport costs, high compression ratios must be achieved, without the fibrous mat being damaged.
The rolls of mineral fibre mats, which it is possible to obtain with winding machines of the prior art, are limited, in the case of specific masses of 8 to 10 kg/m.sup.3, to compression ratios of less than 7/1, if compression is carried out in a single operation, and to ratios of between 6 and 8/1, with methods comprising two mechanical steps or one mechanical step and one vacuum step.
Existing winding machines are of two types: either the elements between which winding takes place are essentially plane elements or winding takes place within a substantially circular cavity.
Some of the winding machines which use two plane conveyor belts forming a dihedron with an aperture of, for example, 60.degree. and within which the winding of the fibrous mat takes place, employ compression plates.
Thus, European Patent Application Serial No. 672 014 employs a double device both for causing the compression of the mat and for making winding easier. On the one hand, a conveyor band and, on the other hand, a plate are used. The conveyor band is not, as is customary, carried and driven by two rollers, but the second roller is replaced by a cylinder of small diameter, thus making it possible to introduce the conveyor a long way between the last turn and the mat portion following the latter. The device comprises, moreover, a plate which ensures that the mat is both compressed and held in the compressed state.
These two elements, namely the &lt; tapered &gt; conveyor and plate, are rigidly connected and move away upstream of the approaching mat as the roll increases in diameter.
European Patent Application Serial No. 374 985 has likewise provided a plate associated with a band conveyor. Its function is merely to maintain the compression produced by the conveyor band which it succeeds. Here too, the assembly is associated rigidly and advances upstream when the roll being formed increases in size.
European Patent No. 551 228 describes a winding machine intended for winding a fibrous mat on itself. It is of the type which employs two belts surrounding the entire roll being formed; it comprises means for compressing the fibrous mat, such as two plane band conveyors, which approach one another, thereby forming a dihedron of small aperture. The essential feature of this winding machine is two belts of which one embraces substantially half the circumference of the roll being formed and the other a large part of the rest. The winding speed and the compression ratio possible without the fibrous mats being damaged are excellent. It became clear, however, that it was still possible to improve the operation of the preceding winding machine.
As described in European Patent No. 551 228, the winding machine has, in fact, an exemplary embodiment in which the state of compression of the fibrous mat, compressed by the two band conveyors mentioned above, is maintained by means of a plate. In fact, the mat is compelled to slide under the plate which is parallel to the conveyor supporting the already compressed mat. Among the variants of the prior winding machine which have been presented, the one comprising the sliding plate is an improvement when compared with the other variants. However, this plate fully performs its function only at the commencement of winding; when the roll increases in size, the distance between the end of the plate and the already formed first turn of the roll increases, and this may allow some decompression of the mat.
The technique of the invention was developed in order to overcome this slight disadvantage.